Consolidated Statements Of Net Income (USD $) In Thousands, except Per Share data	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Consolidated Statements Of Net Income [Abstract]
Revenue	$ 465,617		$ 380,187		$ 1,324,917		$ 1,045,665
Expenses:
Direct operating	310,101	[1]	255,449	[1]	917,687	[1]	722,204	[1]
Marketing	7,723		7,811		20,697		16,375
Research and development	3,239		1,699		7,539		4,928
General and administrative	40,076		37,655		114,795		101,053
Depreciation and other	38,154	[1]	30,626	[1]	106,918	[1]	93,054	[1]
Amortization of intangible assets	685		756		2,055		2,620
Litigation settlement							5,379
Total expenses	399,978		333,996		1,169,691		945,613
Operating income	65,639		46,191		155,226		100,052
Other income (expense):
Foreign currency and other, net	(553)		(130)		(1,004)		(177)
Interest income	1,008		48		1,200		135
Interest expense	(6,424)		(8,741)		(20,078)		(27,167)
Total other income (expense)	(5,969)		(8,823)		(19,882)		(27,209)
Income from continuing operations before income taxes	59,670		37,368		135,344		72,843
Income tax expense	(22,544)		(15,969)		(51,915)		(29,364)
Income from continuing operations	37,126		21,399		83,429		43,479
Loss from discontinued operations, net of tax			(1,894)		(11,068)		(4,165)
Net income	$ 37,126		$ 19,505		$ 72,361		$ 39,314
Basic earnings (loss) per share:
Continuing operations	$ 1.23		$ 0.68		$ 2.72		$ 1.38
Discontinued operations			$ (0.06)		$ (0.36)		$ (0.13)
Basic earnings per share	$ 1.23		$ 0.62		$ 2.36		$ 1.25
Diluted earnings (loss) per share:
Continuing operations	$ 1.18		$ 0.66		$ 2.61		$ 1.35
Discontinued operations			$ (0.06)		$ (0.35)		$ (0.13)
Diluted earnings per share	$ 1.18		$ 0.60		$ 2.26		$ 1.22
Weighted average shares used in basic per share calculations	30,224		31,411		30,608		31,364
Weighted average shares used in diluted per share calculations	31,596		32,382		31,957		32,179

[1] (1) "Direct operating" excludes depreciation and other of $30.1 million and $89.4 million for the three and nine months ended September 30, 2011 and $26.7 million and $83.5 million for the three and nine months ended September 30, 2010.